1. Field of the Invention
This invention relates to an inkjet printing apparatus and a printing method for reciprocating a print head in the main scan direction crossing the direction of feeding a print medium so as to print an image.
2. Description of the Related Art
In a printer that ejects ink drops from nozzles of the print head to form dots on a print medium in order to print an image, filling a certain area with a single color requires printing of dots in the print-required area at a high print density. In such a case, the ejection of a large amount of ink raises the possibility of printing of a blurred outer edge of the print-required area because the ink spreads beyond the print-required area. To solve this disadvantageous problem, Japanese Patent Laid-Open No. 2003-011337 discloses a technique of using ink having relatively high permeation properties (hereinafter referred to as “high permeation ink”) to form dots in the interior area of the print-required area, and using ink having relatively low permeation properties (hereinafter referred to as “low permeation ink”) to form dots in the outer peripheral area. Further, Japanese Patent Laid-Open No. 2003-011337 discloses the arrangement to firstly form dots positioned in the interior area and then dots positioned in the outer area in order to more clearly depict the outer peripheral edge of the print-required area.
However, problems as described below arise in techniques for printing by use of ink of two types differing in permeation properties as described above. In the case of bidirectional printing by use of two print heads, one ejecting the high permeation ink and the other ejecting the low permeation ink, lined up in the main scan direction and of all the nozzles, the printing order of ejection of the high permeation ink and the low permeation ink is changed between printing in one direction (the going direction) of the reciprocation and printing in the other direction (the return direction). As a result, the image quality is changed with the scan direction.